Magnetic material



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WWWWW WWW W P PERMEABILITY 1m 24, 1930. 5, w, ELMEN 1,768,237 namzcIM'BRIAL I 4 Filed Aug. 1925 5 Shoots-Sheet 5 v r I I I r r r r I l I II r I 1 l 1 I I I I r I 1 r I I I I I I r 1 I 1 I I 1 I 1 r I I I 1 r II4 by M 4 3 Patented June '2 1930 j "UNITED S TAf-T ES PATENT; dormer:

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ensrar w. or mourn, aw mnsnr, ASSIGNOR 'ro wnsrnan anaemic or maw YORK,N; Y.,

A conromrron on NEW YORK menn ric 1mm.

Application M August 5, 1925.. Serial No. 48,188.

This invention relates to new materials or substances having certaindesirable magnetlc qualities, among'which are high magnetic permeabilityespecially at low magnetizing forces,

and low hysteresis and eddy current losses.

- It is the principal object of the invention to providefa magneticmaterial which will be particularly suitable for use under conditionswhere'the magnetizing forces are very small,

such as is the case, for example, in the inductive loading of signalingconductors to increasetheir range and speed of operation.

Another object relates to applying this loading material'to a conductivecore in a manner to produce a highly eflicient transmission line forlong range, Another object is toimprove the electrical and 'magneticproperties of magnetic materials of the type useful for loadingsignaling conductors and in particular to increase their resistivitywith vno-material decrease or an actualincrease of their ermeability atlow magnetizing forces an with little increase or with an actualdecrease of-their hysteresis losses. These and other objects j willbecome apparent on consideration of examples of practice thereunderwhich will be disclosed specifically" in this specification,

with the understanding that the definition of the invention will be.given in the appended claims.

This application is in part a continuation of application. Serial No.486,009, filed July 20, 1921, now patent 1,586,883, granted une 8 Iron,because of its quality of high mag netic permeability has always beenconsidered indispensable for the cores of tractive electromagnets, fordynamos, motors, telephone receivers, telegraph .relays, etc;

Silicon steel exhibits magnetic qualities superior to ordinary. ironinsomev respects, but its employment is limited by its comparativebrittleness and the difiiculty of working iron are nickel and cobalt butthey are far high speed signaling.

' continuation of my atomic weights and? atomic numbers and in thisspecification the five elements manganese, 11011, cobalt, nickel andcopper, having the consecutive atomic numbers 25, 26, 27, 28 and 29 willbe referred to as constituting the mag- .netic group of. elements.

The present invention relates to improvements in magnetic materials ofthe type useful for application at low magnetizing forces such as arefound in the magnetic materials employed in continuous loading ofsignaling conductors, and similar applications, as distinguished frompower apparatus. However, the-invention'has to do generally with new andimprovedmagnetic materials and theirutilization. in any commercialapplication where they. are found useful is within the scope of theinvention.

' In my Patent 1,586,884, ranted June 1, 1926 on an application whic'was in part a co nding application, Serial No. 111,080, filed July 24,1916 there is described indetail an improved magneticmaterial-consisting of elements of the .so-

called magnetic group, for example, nickel unit. In the Patent No.1,586,883 previously referred to, there is described and claimed broadlya somewhat similar magnetic material in which a substance is added forthe pur pose of increasing resistivity. These magnetic materials arepeculiarly suitable for use in the loading of long telegraph cables asit. A good quality of soft iron has'therefore described in a patent toO. E. Buckley 0.

been commonly employed as the best magnetic 1,586,874, granted June 1,1926.

The claims attached to the present specification are based in part uponcertain species ofinvention .divisible from those claimed in '80 Othersuitable substances for increasing resistivity of iron-nickel magneticWithout seriously impairing their initial per- 7 force.

ironmickel compositions in and-' scarcity ren er gredlents of magneticthe patents mentioned above and in ,part upon certain newly discoveredfacts not set forth therein. Prior to applicants researches eventuatinin extensive application of iron-nickel al oys, metals such as chromium,molybdenum, man anese, cobalt and silicon had not been em oyed inmagnetic alloys composed of -two e ements of the magnetic group,especiallyof nickel and iron, for their utility. as

rovin or usem applications involving small ma etizing forces. Suchmaterials when com ined with iron and nickel, for example, had beenemployed for the purpose of making hard steels such as tool steels,anti-corrosive steels, and magnetic bodies of great ma etic retentivityand corrosive It as been discovered, with respect to chromium, whichisclaimed broadlyas an ingredient of similar magnetic compositions inPatent 1,586,883, that here is 'a preferred range of chromium contentnot set forth in said patent. Addition of chromium within this preferredrange enhances the beneficial results obtained from its use. It has alsobeen discovered that variation of the chromium content over thispreferred range,

the purpose of im' magnetic materials keeping the nickel content and theheat treatment constant, gives a content. For dlfierent heat treatmentsthe maximum initial permeability is at a different chromium content.There is forth for the' first time a body of systematic data upon themagnetic properties of ironnickel-chromium compositions at lowmagnetizing forces in correlationwith data upon their resistivity.Equivalents for chromium have also been investigated. It has been foundthatjmolybdenum, for example, combines with-ironand nickel withresultssimilar-tothose secured in the case of chromium alonafj -Forthe'purposes of the present specie ficatio'n'. the. chromium groupincludes the metals chromium, mol bdenum'and tungsten, Uranium istheoretica ly deemed to be a member of the chromium group but for allpractical purposes connected with the present invention, it. is excludedfrom consideration.

meability' are manganese, silicon and cobalt. These elements are notedto be of hi h melting point, that is, above 1150 C. form sohd solutionswhen combined with amounts within the scope ofjthe present-invention.The so- .:called noble or raremetals are excluded from the scope of thisinvention even though they have high meltin points, because their costthem unavailable as incompositions: Hence, when reference is made tometals of melting point above 1150 C. it is unders'toodthat resistivityof the alloy.

an extremely high permeabilit full benefit of the maximum range of'in-1t1a1 permeability around a certain Cl'll'OlIlllllIl here set the loysey also ruthenium, rhodium, palladium, osmium, iridium' and platinum, aswell as uranium, are excluded for the purposes of this specification. v

The present invention relates to a further improvement in this material.and provides a new magnetic material comprising elements of theso-called magnetic group combined in suitable proportions and to whichadditional material has been added which increases the This alloy whensubjected to a proper heat tr'eament' and guarded against undue stressesand other disturbing causes not only'develop's and retains at lowmagnetizing forces of the order 0 a few tenths of a c. g. s. unit but atthe same time has low hysteresis and Furthermore it can-be applied withadvantage-to the continuous loading of signaling conductors in such amanner as to obtain the above noted desirable properties.

eddy current losses. f

The invention may be more clearly under- I stood--'"=by reference to theaccompanying drawing in which Fig. 1 comprises curves showin thevariations in initial permeability of a nickel and iron alloy containingapproximately 78 various amounts of the iron content are replaced byequal amounts of a third substance, in this case, chromium.

Fig. 2 shows the variations in maximum permeability under conditionssimilar to those of Fig. 1.

Fig. 3 is a curve showing the variations in initial permeability ofa'magnetic material with variations in the proportions of nickel andironwhen a third substance is held at a constant percentage. I Fig. 4 showsthe variation in permeability of a preferred composition of this materiacom ared with Armco iron and "a high per- -to an alloy of nickelandiron.

Fig. 6 shows-tlir variation in resistivity when'the percentage ofchromium is maintained constant andfthe ratio of nickel and iron varied.

Fig. 7 comprises magnetization curves for various compositions of thismagnetic material in comparison with similar curves for a highpermeability nickel-iron alloy and for Armcoirom f Fig. -8 comprisescurves showingthe variations inpermeability with varying magneticvinduction of the preferred composition as compared with the materialsof Fig 7.

Fig. 9 shows half of a hysteresis oop of the improved magnetic mate 'alcompared with )dia rammatically.

- the curves n1ckel-iron alloy and Armco iron under similar conditions.

Fig. 10 is an elevation of a conductor loaded with the improved magneticmaterial of this invention.

Fig. 11 is a cross-s ctional view of the same. a

Fig. 12 is a cross-section of the same conductor when embodied in asubmarine cable. Fig. 13 is a sectional view of a type of furnacesuitable for annealing the loading conductor. Fig. 14 is anelevation ofa conductor wrapped with two'layers of this magnetic materia i Fig.

5 shows a loading coil with its core of this material and its. windingsindicated eferrin now more particularly to Fig. 1,

i and B show the effect upon the of a magnetic alloy comel and 21%% ironwhen of a third substance,'in

initial permeabilitv prising 78 nic varying percentages this casechromium, equal amount of iron, curveA being for one heat treatment andcurve B another.

The initial permeability as defined in my copendin'g applicationreferred to above is the permeabilit for zero magnetizing forces. Thisvalue is o tained by determining a series of values for exceedingly lowforces, say of the order of .01 to .050. g. s. units. The results plotlinearl. and may be extrapolated back to the value or H=O, thus givingthe g'alue of permeability for zero magnetizing orces.

- The heat treatment for curve A consistedin annealing by slow coolinfrom 1100 0., followed-by heatingto 600 termined rate, namely, 9.5 persecond. In accordance with a slight modification of this heat treatmentgiving the same results, the material is-first heated to the desiredtemperature and then cooled slowly to a temperature near' the magnetictransition temperature a and thencooled rapidly at a predetermined ratewhich is and a rate at which undue stresses and strains Wlllbe set up inthe materials. Curve B represents the same conditions as curve A- exceptthat the heat treatment consisted only of the annealing.

The proportions. of 78 72; nickel and 21 iron were selected forpreliminary tests since approximately these proportions in initialpermeability. When he material reaches a inaximum whenslight -2% cromiumby weight is used- ,creases rapidly with larger amountsof amination ofthis curve itwill the maximum are added to replace an and then coolmg toroom temperature at a rapidpredeintermediate an annealing rate,

is given the double heat treatment as represented curve A the initialand'then dechromium. In the case 0 the single heat treatment as shownby-cu'rve B- the maxi'- mum-initial permeability is reached when thematerial contains approximately 4% chromium by'weight and decreases lessrapidly with lar er amounts of chromium.

The e ect upon the maximum "permeabil- Permeability y more than ity ofan alloy containing 78 nickel and 21 iron when varyingamounts of theiron are I mium is shown graphically in Fig. 2.- In obtaining the dataforcu'rve A the magnetic material was subjected to the same double heattreatment as was used in resented by; curve A of Figfl. From anexpermeability decreases very rapidly with an increase of chromium. Thusfor an alloy containing 1% chromium there was obtained a maximumpermeability of replaced by equal amounts of chrothe test rep- 85. beseen'that 1 150,000, for an alloy containing 2% chromium the maximumpermeability was decreased to 60,000 and-for'an alloy containing Y 0 Ichromium, the maximum permeability is approximately 10,000. {When themag-- ne'tic material is subjected to a single heat treatment asillustrated by curve B,the maximum permeability.increases with the chr0-mium content'until a chromlum content of approximately is reached, themaximum permeability then increases rapidly: and

the curve crosses curve A (which relates tothe same composition giventhe double heat treatment) and remains above the curve A until thechromium content approaches 7%.

As a' result of the discoveries represented by the curves of Figs. land'2 it was seen that an alloy containing approximately 2% chromium, whenproperly heat treated would be very satisfactory from the standpoint ofpermeability.

.- In order to obtain a further indicatlon,

then, of the most satisfactory proportions of nickel and iron, thoroughtests were made in which the chromium content was maintained constantat- 1.9% and the proportions of nickel and iron varied, The results ofthese tests which are shown on Fig. 3 indicate that the mostsatisfactory results are obtained with approximately 78 75 nickel andthe balance iron and a third substance of which chromium is the specificexample dealt with in the present instance. As indicated by the curve ofFig. 3, the initial permeability curve rises very rapidly as the nickelcomponent approaches 5%, reaching a maximum at approximatel creasingrapi 1y with further increases in the nickel content. These tests weresupplemented by tests on other nickel-iron chromium al- /2% nickel andthen de-.,

' Y creasing material v and other similar loys containingliup1 to 8%chromium and in -'each casethe g est permeability was obtained when thenickel content was approximately 7 8%%. Similar tests were also madewith substances other than chromium. For example, with: small amounts ofcobalt, silicon, manganese and molybdenum, as high or higherpermeabilities were obtained when the nickel content was approximately 78 of the whole as when any other rcentage was used. The expressionreslstance 1nwill be used hereinafter to include metals of melting pointabove 1l50 (3., such for example, as chromium, molybdenum,

common metals and combinations of these elements. The addition of stillother elements or substances for the same or other pur' oses, therebyproducing compositions within the scope of the appended claims, is notdeemed to be a departure from the invention.

In Fig. 4 are curves showing variations in alternating currentpermeability of various magnetic materials when subjected to a 200 cyclealternating current ma netizing flux of- .001 c. g. s. units and uponwhich is superimposed varying direct current magnetizin forces. Curve Ashows the permeability 0 an alloy containing 7 8 nickel and 2l iron.Curve B shows the improved magnetic material containing 781/ nickel,1.9% chromium and the blance iron and curve shows the alternatingcurrent permeability of a very pure grade of magnetic iron. From thesecurves it will be seen'that the improved magx netic material containingapproximately 2% chromium when subjected to a superimposed directcurrent magnetizing force within the limits employed in this figure hasa considerably higher alternating current permeability than an alloycontaining 7 8 mckel and the balanceiron, and has a decidedl hi her A.C. permeability than the best gra e o magnetic iron. The importance ofthis characteristic of the material is apparent since loaded lines andvarious kinds of apparatus such as relays,

5 tivityof an alloy telephone receivers and repeating coils areconstantly subjected to a greater or lesser direct current magnetizingforce upon which is superimposed a varying magnetizing force resultingfrom voice andsignaling current.

In Fig. 5 is shown the variation-a'fi resiscolltaining' 78%%fnicbl andthe balance iron chromiumfior difierent proportions of "the latter twoelements.

(It willbe noted that oit the alloy increases rapidly with an' increasein' the of chromium present in the alloy. r

The curve of Fig. .6 shows theyariation in resistiv y of an we mt 'sappr x the balance nickel and iron with varying proportions of thelatter-two elements. .Asshownbythiseurve the maganese, cobalt andsilicon,"

variation in the nickel contentproduces slight change in the resistivityof the material.

The curves shown in Fig. 7 comprise a seriesof magnetization curves forthe improv magnetic alloy with-various percentages of chromium in comarisen witha nickel-iron alloy containing 8 nickel and 21%% iron and avery pure grade of magnetic iron. The nickel-iron alloy and the variousnickeliron-chromium alloys were 'ven the double heat treatmentpreviously re erred to and the iron sample was heat treated to bring outits best magnetic characteristics. Curve A is the magnetization curvefor the nickel-iron alloy containing 78 nickel and. 21 iron. Curve B,which is the improved magnetic material containing 7 8 nickel andapproximately 2% rises less rapidly thancurve A except at a point nearthe origin and saturates at a considerably lower value. Both, however,are far above the curve for Armco iron as represented by curve C whichhas not even begun to rise steeply at the low magnetizing forces withwhich we are now chiefly concerned. Curve D is a magnetization curve fora nickeliron alloy containing approximately 7 8 nickel, .98% chromiumand the balance iron. Curves E, F and G are for similar alloyscontaining respectively 2.37%, 3.86% and 6.85% chromium. These curvesshow that for a given magnetizin force above .025 c. g. 5. units, thepermeability is decreased with an increase inthe chromium content. Italso may be'seen that the magnetizing force necessary to p oduce maximumpermeability increases wit an increase in t e chromium content.Additional tests made with the same samples (not shown in the drawing)indicate that with extremely slow cooling (annealing in the furnace)practically the reverse is true, the permeabihty for a given magnetizingforce increasin with increase in the tent an the point of maximumpermeability being decreased with. an increase in the amount of chromiumpresent. These tests further show that alloys containing 3% or more ofchromium are less sensitive to heat treatment than are those containingless chromium. Therefore, by using alloys containing larger amounts ofchromium, it ispossiblgt'o obtain a more uniform product under ordinarycommercial process although this uniformity is obtained at a sacrificeof permeability.

The curves of Fig. plotti'n the rmeabi 'ty values of the materials 0Fig. against the'valies of magnetic induction. 1 Curve A is, the curvefor mckelron allo containing 7 8 5% nickel and 21%% 11'011'. urve B isthe curve for the chromium with the balancev iron, I

chromium con- 8 are obtained by a material in which approximately 2% ofthe the curve-{or Armco iron under similar 00nditiom.

- The hysteresiscurves of the three materials of Figs. 7 and 8 are shownin Fig. 9, only the upper half of thecurves being shown.

These curves are carried to a maximum induction of 5,000 0. g. s.units'a-nd are'drawn on the same scale. Curve A is half of thehysteresis loop of the nickel-iron alloy containing 78 nickel and 21 70iron. Curve. B is a similar curve foran alloy represented by curve A iniron is replaced. by an equal amount of Hchromium and curve C is asimilar curve for Armco iron; The hysteresis loop for the imcontainingchromium, while in this particular case slightly less than that of thesimilar alloy without chromium, is reall I of the same order but bothhave a very muc smaller area (about than that of the loop of curve C forArmco iron.

I't'will also be noted from a'study of the curves of Fig. 9, that thecoercive force of the improved magnetic material, although slightlyless, is of the same order as the coermately 2% cive force of thenickel, 21 73 iron, coercive force for iron as represented by curve C.After being subjected to a magnetizing force of 100 c. g. s. units, thecoercive force of the nickel-iron alloy containing 7 8 nickel and of theimproved magnetic alloy containing approxi chromium is of the order of.05

alloy containing 7 8 5% and is much less than the c. g. s. unit, whereasthe coercive force for H terial in its may be fused together in aninduction furnace, in the and 78$ of these materials pose, and to thisalloy is then added the t ird Armco iron is approximately .86 c. g. s..unit. In the preparation of this magnetic ma preferred form, iron andnickel proportion of about 19%, iron nickel, good commercial gradesbeing suitable for this ursubstance such as chromium; which increasesthe res1st1v1ty of the materlal. However, 1n

order to prevent excessive substance from going into amounts of this theslag, it has been found preferable to first make up an alloy of thatsubstance with nickel and then add that alloy to a nickel alloy, soproportioncd as to'give a desired proportion tothe magnetic materialwhen the two alloys are combined. Forcxample, "make anlckel-lron-chromlum alloy containwhen-it is desired to ng approximately2%,,chromium, an. alloy I of approximately 75% mium is first pre ared toa molten nic el-iron alloy while in the to the material. After the threenickel and 25% chroand this alloy is added furnace soas to give thedesired proportions ingredients Poured in a r are added the.'compositionis bar or rod mold and cooled to form a thic which is then rolled,swaged or otherwise A suitable process for making and treating.

.worked into the form in which it is to be used.

the material is disclosed in patent to J H. White, No. 1,586,871,granted June" 1, 1926.

which approximately 2% of the,

the best grade ofmagnetic' tape, the drawing process When the materialis to be used for the con-' tinuous loading of signaling conductors, thebar or rod as jected to repeated swaging and annealing operations'or tohot rolling "by which iti's reduced in diameter and correspondin lyelongated. The long rod thus formed is tfien drawn outby repeateddrawingand annealing operations to a size about #20 B and S gage and is thenformed'into passing it between flattening rolls and by several suchoperations flattening it to a tape having a thickness of about a width alittle more than .125 inches. In the last annealing operation thematerial is heated to a temperature of ll00 C. and then allowed to coolslowly thus carrying out the first step of the heat treatment which isnot completed until after the tape is wound upon the conductor. Thistape is next passed through cutting rolls or discs which trim its edgessquarely on both sides and give the tape an exact and uniform width,thus placing it in condition for application upon the conductor. When itis desired to use the loading material in the form of wire, rather thanis continued'until the wire has the desired dimensions:

The stranded conductor of F igs'. 10 and 11 comprises a centralcylindrical wire 21 enveloped by six surrounds 22, which are shapedannulus about the central wire. It is desirable that the conductorassembled in this way have a smooth cylindrical contour and for thispurpose it may be drawn through a die or subjected-to a swa gingoperation. The stranded conductor as described has the advantages offlexibility and preservation of conductive continuity in case ofbreakage of any of the strands by a force not too severe to disrupt allthe strands at the same lace. This stranded-conductor 21--22 is. #5 gand S gauge in size and is loaded with the inn-- proved magneticmaterial in the form of tape as described above. is wrapped helically onthe stranded copper core in accordance with my copending appli nowPatent No.1,58.6,887-, grante June 1,

I 1926, care being taken to abut the edgesclosely Iwithout overlapping.App

the final step in its h'eat'j treatment and for u'rpose it is drawnlengthwise through this a thin tape by.

.006 inches and The magnetic tape 23 taken from the mold is sublll .aratus for acconi- ""plishing this'is described in detail in patent thef urnace of Fig. 13' which is maintained at a tem erature of about 900C. This is a mufile *urnac'e with the heating elements 26 betweenthefire cla' "mu'flie 27 and the fire brick 28. Around t iron outer wall.perlining 30 the e firebrick 28 is a sheet r I The iron tube '29 has acop inside diameter of which no jects about eightinches beyondthefurnace is about two is a little over. one-half inch. Itextends clearacross the furnace The length ofthe pass through the feet and the rateof movement of the conductor therethrough is about three quarters of afoot per minute. the taped wire passes from the furnace and theprojected ends of -the air which about normal room temperature, that is,about 20 C. Under the conditions and for the dimensions described, thisgives a proper rate of cooling. after heating in the furnace. Theconductor should be led awa straight from the furnace for a suflicientdistance to ermit it becoming well cooled, since bend- 1 g at this stagemay impair its permeability. o the necessary coiling of the tapedconductor should be on a large radius not less than two feet, since .thestrains involved in coiling and uncoiling on a smaller radious may lowerthe permeability. After the heat treatment,

walls.

the taped conas' ductor is first insulated in such a manner that theloading material will not be subjected to uneven strains when the cableis submerged at great depths. This is preferably accomplished by coilingthe taped conductor with liquid bitumen in accordance with the processdescribed in detail in a copendmg application of Archie 61 ,511, filedFebruary 7 1923, now Patent No. 1,700,766, grante H85 insulated,armoured and mechanically remsubmarine cables by I wrapping of ute and40 of. different diameter forced according to the usual practice. for Isurrounding it with a layer of guttapercha and then with the usualgiving the product as shown in cros section in Fig. 12.

-While a certain speed and temperature of 'a certain type of furnacehave been described I to produce the desired results inthe case of aparticular cable, it is apparent that these factors ma be varied oradjustedtomeet different con 'tions, such for example, as a cableclosed:

sions of the conductive core and the width and cross sectionbf' theloading, s cifically for a certain-contemplated examgle of a long gra htransmission; I the r sheath is desired, it may be best to apply it opto directions one outside the other as ing ted i I and the fact that thelayers.

furnace at each end and pro-.

rents, but this coating may I thickness or insulating coatings. As maybe applied to-the loading material if the tube 29, it cools n. outsideof the tubeis kept at low coercivity,

R. Kemp, Serial No.-

eb.5,1929. Itisthena sheath of steel wires,

from the one here dis- 1n A description has been given of -the markablysaving of material 10 for-high speed tele-" In somecases where a..ceiving up ratus. v I

I I coilssmallwiresofthemagthe form of two tapes wound in-the'advantages manner of ing coils.

likely to slip or buckle.

When more than one I coating of oxide on each serves as. an insulatingmaterialfor reducing'the.eddy curajp p s y creased in desired.

With a conductor composed I proved magnetic material containingaproximatel 2% chromium the attenuation osses are ept low since not onlydoes the material have a cause of its hi h resistivity, the eddy lossesare also ept at a The improved magnetic material of this inventionisuseful for-other purposes than for the continuous loading of signalingconductors; For example, it may be I vantagepusly' in the magneticcircuits of telephone receivers, ringers and electromagnetic devices ofvarious types. Because of its it isof particular importance in themagnetic circuits of moving vane meters,-ma rginal relays, split phaserelays, and similar devices in which the sensitivity of operation isinfluenced to a considerable degree by the'previous magnetic history ofthe magnetic members. The low saturation point and the shape of themagnetization curves make'this material extremely well adapted for usein the cores of frequency changers and magnetic modulators. teristicsare such as :to able material for thelcores of various types of Also,its characof the immake it a very'desir- 100 low hysteresis factor but,becurrent used adtransformers, such, for example,as those used forcurrents having connectedio the line. 7

on used inthe cores'o which are continuall Another use for'whic it is'cularly adapted, is as a magnetic shiel for shiel one magnetic fiel aparatus from extranetransmisslon of music and the voice. Be-

a'wide'fre- (fluency rangesuch as those which occur in t e lumploading'as well. as for continuous loadand low ma small volume made upin rewith a consequent and low cost of manufacture. Coils with coresofthis materialjhave magnetic shunts in the core .32 on winch 3 8..and'34are indicated Chokecoilsj of vergahigh inductance I I the well known y..Incrderto f been found particularly valuablefor use as submarinetelegraph, re-

Such a eoil is'- u'o it isalso-useful for/ magnetic materials thismaterial, it is,

acterized in that t ability even though large currents are superimposedon the loading coil circuit, the core may be provided with gaps filledwith nonof the non-magnetic gaps with the windings thereon may be heldtogether by means of clamps 37. i

Although for commercial reasons it'will probably be advantageous'toemploy a single element as the substance for increasing the resistivityand the initial permeability of of course, obvious that several elementscould be simultaneously employed to obtain one or more of the advantagesas set forth in the specification without departing from the spirit ofthe invention. Iron,'in accordance with this specification,

means iron as described in the literature. of

' prior to August 1, 1925. a What is claimed is: l

, 1. A magnetic composition comprising at least two elements 0 themagnetic group and other metallic substance composed of, metals ofmelting point above 1150 C. which when added to magnetic compositionscomposed of such two elements increases the resistivity, characterizedin that the proportion of such'other substance is such as not todecrease the initial permeability.

2. A composition in accordance with the foregoing claim, furthercharacterized in that the elements of the magnetic group include nickeland iron. e

3. A composition in accordance with .the second foregoing claim, furthercharacter- 1zed in that the elementsof the magnetic group are nickel andiron and the other substance is in a proportion which increases theinit-ialpermeability.

4. A magnetic compositionin accordance with the third foregloing claim,further chare elements of the maginitial permeability obtained by theadded substance is higher than that of lron.

5. A magnetic compositionin accordance i with-thefourth foregoing claimin which'the "elements of. the magnetic group are nickel andi'ron,'c'haracterized in this that the initial permeability ofthe comositionwhen heat treated to produce high lnitial permeability is higherthan can be produced by heat treatmg. the composition with theothersubstance replaced by iro 6; A magnetic composition of initial pertmeability higher than ironcomprising nickel and iron,.the nickel beingmore than-% of the whole and including other metallic of non-magneticmaterial and the core sections on each side the whole,

up in the material.

substance of melting point above 11509 C.-

whereby the resistivity of such compositions. is increased. Y V

- 7. A composition in accordance with, the foregoing claim in which thenickel is from to of the composition." j

n 8.". A magnetic material comprising nickel, iron, and a third metallicelement of melting pointabove 1150' C. to increase the specificresistancev thereofand in which the nickel component is Whole. I

approximately 78 /2% o fthe 9. A magnetic material comprising nickel, i

and iron to which is added chromium in such amount as with propertreatment will produce higher initial permeability. than when the nickeland iron alone are present.

10. A magnetic. material comprisin'g approximately 7 8 nickel, and theremalnder iron and chromium in such amount as with proper treatment Willproduce higher initial permeability than when the chromium is replacedby iron. 1 11. A magnetic material heat treated to have highpermeability in a very low range of magnetizing forces comprisingnickel,

chromium and iron in which'the nickel com-' ponent consists ofapproximately 78%% of greater than '7 of the whole and the balance iron.I

12. A magnetic material comprising nickel, chromium and iron in whichthe nickel component consists of approximately 78 0f the whole, thechromium component not more" than 2%% of the whole and the balance iron.13. A magnetic material, comprisingta proximately 78 92; nickel,approximate y resistance than if said other element were replaced byiron.

15. A magnetic material complil' ising nickel, iron, and not to exceed7%-- c nickel component being morethan 70% .ofthe whole,' said magneticmaterial having those netie group include nickel and iron and, theproperties which are produced in such a composition b beingannealedat-atemperature of thei or er'of' 1100 C. and slowly 'eooled" therefromfollowed bringing the niate and then" cooling rapidly to a temperatureconsiderably'lower than 600 C. at a ratemthe chromium component notomium, the n termediatean annealing rate and a rate at which unduestresses and will set 16. A magnetic material comprising nickel,

' chromium and iron in which the nickel component comprisesapproximately 78 of the whole, the chromium component not to exceed 7%of the whole, and the balance iron, :said material having themagnetic'properties which are produced by heatingsuch a compoponentcomprises approximately 78 /?r peraturc,

' 78 nickel, ap

pointoi the material.

'- go s. umt.

sition to 1100 heating to 600 point lower C. and slowly cooling, then C.and cooling rapidly to a than the magnetic transition 17 A magneticmaterial comprising. nickel, chromium and 1 I0I1 in which the mo elcomthe whole, the chromium component om 2 to 5% of the whole, and thebalance iron, said material having the properties which are produced insuch a composltion bein C. an O. and

cooled slowly.

' 18. A magnetic material comprising approximately 7 8 nickel, chromiumbetween about 1% and about 5%, and the balance iron, said magneticmaterial having the magnetic properties produced in such amaterial byitsbeing heated above a certain temcooled slowly to a temperature near themagnetic transition point for that material, and then cooled rapidly ata rate intermediate an annealing rate and a-rate at which undue stressesand strainswill be set up in thematerial.

19. A I magnetic material comprising a proximately 7 8 'nickel,approximate y 2% chromium," and the balance iron, said magnetic materialhaving the pro rties produced in such a material by its ein heattreatedby slowly cooling from 1100 lowedby heating to 600 C., and then coolingrapidly to a transition point of the material. 7 p

20. A magnetic material comprising? nickel, iron and at least one othermetallic element of melting point above 1150 C. in an amount notover'10% to give the material increased initial permeability, and

in. inductive relation with said material, means whereby the conductoris caused to carry a current sufiicient to produce in the-material amag-j netizing force notexceedin'g'a fraction of a balance iron, and in21. A-magnetic material comprising proximately Bl/ nickel, .approxim 2%chromium, and t combination therewith an electrical oonductorininductive 'relation' with said material. .22. A loaded conduotorcomducting 'coreihaving alayer .o'f oading rial wrapped helically.thm&b0ut,"Slld load-.- ing material consisting roximatelyf2% chromiumand approximate ISM/ 1ron, th'e loadedconductor being .su jected .to aheat treatment to develop its optimum-ma etic qualities.

23. A magnetic composition comprising.

chiefly two elements'of'the' magnetic grou in lproportions which if usedalone woul 't high permeability to be obtained and including additionalmaterial group f ol-.

point lowervthan the magnetic sistivilz.

magnetic composition of initial per? in combinationtherewith anelectrical conductor meability more constant rising FE Cone ofapproximatelymit high maximum rmeability to be obtained and incluadditional material selected from the metallic elements of melting pointabove 1150 C. whereby thetinitial permeabilit is increased and themaximum permeability is not increased as compared with the same twoelements of the magnetic in the same proportions without the additionalmaterial.

25. A magnetic composition of initial per meability over 200 containingbetween 64% and 85% nickel and the balance chiefly iron plus an amountupto 8% of resistance increasing material selected from metals ofmelting point over 1150 C.

26. meability over 200 in whichnickel is present in an amount between64% of the nickel-iron content and 85% of the entire and the balancechiefly iron plus an amount up to 8% of materialof the c romium oup o'the'periodic table for increasing e re- 27 meability over 200 m whichnickel is present in an amount between 64% content and 85% of theentire-composition, in which chromium is resent in an amount from'1% to8% and t e balance is chiefly iron. r r

28. A magnetic com 'tion'ofinitial permeability over 200 comprisingnickel and iron in proportions in which the nickel comprises from 64% ofthe nickel-ir content'to 85% of the whole and additiona materialselected from the group of metals having a melting point above'1150 'forthe peradditional material. I 29. A magnetic composition of initialpermeability-"over 200 comprising nickel and ironin proportions in whichthe nickel-compri 'fm 6 t0' 85% of the whole up to of the whole selectedfrom the group of metals having a melting point above 1150 C. andforming a nickel-iron 'compounds mounts under 10% for reducing thebyline: sis loss and increasing the constancy. 91181,- meability.

magnet1c composition of initial per-.

composition solid solution with when present -:in'

selected from the metallic elements of meltof thenickel-ironwithouttbeof the nickel-iron content 1 and additional material 30. A compositionin accordance with the foregoing claim in which said additional materialis composed mium cup of the periodic table.

31. magnetic material com 2% chromium, 64% .to 85% nickel and thebalance chiefly iron.

32. A magnetic composition heat treated to develop desirable magneticproperties at low magnetizing forces'comprising chiefly nickel and ironin which the nickel lies between 65% of the total iron-nickel contentand 85% of the whole, characterized in that from to 10% of: the entirecomposition is composed of material selected from the group of elementsincluding chromium, molybdenum, cobalt, silicon and manganese.

' In witness whereof, I hereunto subscribe my name this 1st day ofAugust, A. D. 1925.

- GUSTAEW; ELMEN.

of elements of the chro-,

rising about

